qemu/block/mirror.c
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   1/*
   2 * Image mirroring
   3 *
   4 * Copyright Red Hat, Inc. 2012
   5 *
   6 * Authors:
   7 *  Paolo Bonzini  <pbonzini@redhat.com>
   8 *
   9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10 * See the COPYING.LIB file in the top-level directory.
  11 *
  12 */
  13
  14#include "qemu/osdep.h"
  15#include "qemu/cutils.h"
  16#include "qemu/coroutine.h"
  17#include "qemu/range.h"
  18#include "trace.h"
  19#include "block/blockjob_int.h"
  20#include "block/block_int.h"
  21#include "sysemu/block-backend.h"
  22#include "qapi/error.h"
  23#include "qapi/qmp/qerror.h"
  24#include "qemu/ratelimit.h"
  25#include "qemu/bitmap.h"
  26#include "qemu/memalign.h"
  27
  28#define MAX_IN_FLIGHT 16
  29#define MAX_IO_BYTES (1 << 20) /* 1 Mb */
  30#define DEFAULT_MIRROR_BUF_SIZE (MAX_IN_FLIGHT * MAX_IO_BYTES)
  31
  32/* The mirroring buffer is a list of granularity-sized chunks.
  33 * Free chunks are organized in a list.
  34 */
  35typedef struct MirrorBuffer {
  36    QSIMPLEQ_ENTRY(MirrorBuffer) next;
  37} MirrorBuffer;
  38
  39typedef struct MirrorOp MirrorOp;
  40
  41typedef struct MirrorBlockJob {
  42    BlockJob common;
  43    BlockBackend *target;
  44    BlockDriverState *mirror_top_bs;
  45    BlockDriverState *base;
  46    BlockDriverState *base_overlay;
  47
  48    /* The name of the graph node to replace */
  49    char *replaces;
  50    /* The BDS to replace */
  51    BlockDriverState *to_replace;
  52    /* Used to block operations on the drive-mirror-replace target */
  53    Error *replace_blocker;
  54    bool is_none_mode;
  55    BlockMirrorBackingMode backing_mode;
  56    /* Whether the target image requires explicit zero-initialization */
  57    bool zero_target;
  58    MirrorCopyMode copy_mode;
  59    BlockdevOnError on_source_error, on_target_error;
  60    /* Set when the target is synced (dirty bitmap is clean, nothing
  61     * in flight) and the job is running in active mode */
  62    bool actively_synced;
  63    bool should_complete;
  64    int64_t granularity;
  65    size_t buf_size;
  66    int64_t bdev_length;
  67    unsigned long *cow_bitmap;
  68    BdrvDirtyBitmap *dirty_bitmap;
  69    BdrvDirtyBitmapIter *dbi;
  70    uint8_t *buf;
  71    QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
  72    int buf_free_count;
  73
  74    uint64_t last_pause_ns;
  75    unsigned long *in_flight_bitmap;
  76    unsigned in_flight;
  77    int64_t bytes_in_flight;
  78    QTAILQ_HEAD(, MirrorOp) ops_in_flight;
  79    int ret;
  80    bool unmap;
  81    int target_cluster_size;
  82    int max_iov;
  83    bool initial_zeroing_ongoing;
  84    int in_active_write_counter;
  85    int64_t active_write_bytes_in_flight;
  86    bool prepared;
  87    bool in_drain;
  88} MirrorBlockJob;
  89
  90typedef struct MirrorBDSOpaque {
  91    MirrorBlockJob *job;
  92    bool stop;
  93    bool is_commit;
  94} MirrorBDSOpaque;
  95
  96struct MirrorOp {
  97    MirrorBlockJob *s;
  98    QEMUIOVector qiov;
  99    int64_t offset;
 100    uint64_t bytes;
 101
 102    /* The pointee is set by mirror_co_read(), mirror_co_zero(), and
 103     * mirror_co_discard() before yielding for the first time */
 104    int64_t *bytes_handled;
 105
 106    bool is_pseudo_op;
 107    bool is_active_write;
 108    bool is_in_flight;
 109    CoQueue waiting_requests;
 110    Coroutine *co;
 111    MirrorOp *waiting_for_op;
 112
 113    QTAILQ_ENTRY(MirrorOp) next;
 114};
 115
 116typedef enum MirrorMethod {
 117    MIRROR_METHOD_COPY,
 118    MIRROR_METHOD_ZERO,
 119    MIRROR_METHOD_DISCARD,
 120} MirrorMethod;
 121
 122static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
 123                                            int error)
 124{
 125    s->actively_synced = false;
 126    if (read) {
 127        return block_job_error_action(&s->common, s->on_source_error,
 128                                      true, error);
 129    } else {
 130        return block_job_error_action(&s->common, s->on_target_error,
 131                                      false, error);
 132    }
 133}
 134
 135static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
 136                                                  MirrorBlockJob *s,
 137                                                  uint64_t offset,
 138                                                  uint64_t bytes)
 139{
 140    uint64_t self_start_chunk = offset / s->granularity;
 141    uint64_t self_end_chunk = DIV_ROUND_UP(offset + bytes, s->granularity);
 142    uint64_t self_nb_chunks = self_end_chunk - self_start_chunk;
 143
 144    while (find_next_bit(s->in_flight_bitmap, self_end_chunk,
 145                         self_start_chunk) < self_end_chunk &&
 146           s->ret >= 0)
 147    {
 148        MirrorOp *op;
 149
 150        QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
 151            uint64_t op_start_chunk = op->offset / s->granularity;
 152            uint64_t op_nb_chunks = DIV_ROUND_UP(op->offset + op->bytes,
 153                                                 s->granularity) -
 154                                    op_start_chunk;
 155
 156            if (op == self) {
 157                continue;
 158            }
 159
 160            if (ranges_overlap(self_start_chunk, self_nb_chunks,
 161                               op_start_chunk, op_nb_chunks))
 162            {
 163                if (self) {
 164                    /*
 165                     * If the operation is already (indirectly) waiting for us,
 166                     * or will wait for us as soon as it wakes up, then just go
 167                     * on (instead of producing a deadlock in the former case).
 168                     */
 169                    if (op->waiting_for_op) {
 170                        continue;
 171                    }
 172
 173                    self->waiting_for_op = op;
 174                }
 175
 176                qemu_co_queue_wait(&op->waiting_requests, NULL);
 177
 178                if (self) {
 179                    self->waiting_for_op = NULL;
 180                }
 181
 182                break;
 183            }
 184        }
 185    }
 186}
 187
 188static void coroutine_fn mirror_iteration_done(MirrorOp *op, int ret)
 189{
 190    MirrorBlockJob *s = op->s;
 191    struct iovec *iov;
 192    int64_t chunk_num;
 193    int i, nb_chunks;
 194
 195    trace_mirror_iteration_done(s, op->offset, op->bytes, ret);
 196
 197    s->in_flight--;
 198    s->bytes_in_flight -= op->bytes;
 199    iov = op->qiov.iov;
 200    for (i = 0; i < op->qiov.niov; i++) {
 201        MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
 202        QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
 203        s->buf_free_count++;
 204    }
 205
 206    chunk_num = op->offset / s->granularity;
 207    nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
 208
 209    bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
 210    QTAILQ_REMOVE(&s->ops_in_flight, op, next);
 211    if (ret >= 0) {
 212        if (s->cow_bitmap) {
 213            bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
 214        }
 215        if (!s->initial_zeroing_ongoing) {
 216            job_progress_update(&s->common.job, op->bytes);
 217        }
 218    }
 219    qemu_iovec_destroy(&op->qiov);
 220
 221    qemu_co_queue_restart_all(&op->waiting_requests);
 222    g_free(op);
 223}
 224
 225static void coroutine_fn mirror_write_complete(MirrorOp *op, int ret)
 226{
 227    MirrorBlockJob *s = op->s;
 228
 229    if (ret < 0) {
 230        BlockErrorAction action;
 231
 232        bdrv_set_dirty_bitmap(s->dirty_bitmap, op->offset, op->bytes);
 233        action = mirror_error_action(s, false, -ret);
 234        if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
 235            s->ret = ret;
 236        }
 237    }
 238
 239    mirror_iteration_done(op, ret);
 240}
 241
 242static void coroutine_fn mirror_read_complete(MirrorOp *op, int ret)
 243{
 244    MirrorBlockJob *s = op->s;
 245
 246    if (ret < 0) {
 247        BlockErrorAction action;
 248
 249        bdrv_set_dirty_bitmap(s->dirty_bitmap, op->offset, op->bytes);
 250        action = mirror_error_action(s, true, -ret);
 251        if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
 252            s->ret = ret;
 253        }
 254
 255        mirror_iteration_done(op, ret);
 256        return;
 257    }
 258
 259    ret = blk_co_pwritev(s->target, op->offset, op->qiov.size, &op->qiov, 0);
 260    mirror_write_complete(op, ret);
 261}
 262
 263/* Clip bytes relative to offset to not exceed end-of-file */
 264static inline int64_t mirror_clip_bytes(MirrorBlockJob *s,
 265                                        int64_t offset,
 266                                        int64_t bytes)
 267{
 268    return MIN(bytes, s->bdev_length - offset);
 269}
 270
 271/* Round offset and/or bytes to target cluster if COW is needed, and
 272 * return the offset of the adjusted tail against original. */
 273static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
 274                            uint64_t *bytes)
 275{
 276    bool need_cow;
 277    int ret = 0;
 278    int64_t align_offset = *offset;
 279    int64_t align_bytes = *bytes;
 280    int max_bytes = s->granularity * s->max_iov;
 281
 282    need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
 283    need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
 284                          s->cow_bitmap);
 285    if (need_cow) {
 286        bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes,
 287                               &align_offset, &align_bytes);
 288    }
 289
 290    if (align_bytes > max_bytes) {
 291        align_bytes = max_bytes;
 292        if (need_cow) {
 293            align_bytes = QEMU_ALIGN_DOWN(align_bytes, s->target_cluster_size);
 294        }
 295    }
 296    /* Clipping may result in align_bytes unaligned to chunk boundary, but
 297     * that doesn't matter because it's already the end of source image. */
 298    align_bytes = mirror_clip_bytes(s, align_offset, align_bytes);
 299
 300    ret = align_offset + align_bytes - (*offset + *bytes);
 301    *offset = align_offset;
 302    *bytes = align_bytes;
 303    assert(ret >= 0);
 304    return ret;
 305}
 306
 307static inline void coroutine_fn
 308mirror_wait_for_free_in_flight_slot(MirrorBlockJob *s)
 309{
 310    MirrorOp *op;
 311
 312    QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
 313        /*
 314         * Do not wait on pseudo ops, because it may in turn wait on
 315         * some other operation to start, which may in fact be the
 316         * caller of this function.  Since there is only one pseudo op
 317         * at any given time, we will always find some real operation
 318         * to wait on.
 319         * Also, do not wait on active operations, because they do not
 320         * use up in-flight slots.
 321         */
 322        if (!op->is_pseudo_op && op->is_in_flight && !op->is_active_write) {
 323            qemu_co_queue_wait(&op->waiting_requests, NULL);
 324            return;
 325        }
 326    }
 327    abort();
 328}
 329
 330/* Perform a mirror copy operation.
 331 *
 332 * *op->bytes_handled is set to the number of bytes copied after and
 333 * including offset, excluding any bytes copied prior to offset due
 334 * to alignment.  This will be op->bytes if no alignment is necessary,
 335 * or (new_end - op->offset) if the tail is rounded up or down due to
 336 * alignment or buffer limit.
 337 */
 338static void coroutine_fn mirror_co_read(void *opaque)
 339{
 340    MirrorOp *op = opaque;
 341    MirrorBlockJob *s = op->s;
 342    int nb_chunks;
 343    uint64_t ret;
 344    uint64_t max_bytes;
 345
 346    max_bytes = s->granularity * s->max_iov;
 347
 348    /* We can only handle as much as buf_size at a time. */
 349    op->bytes = MIN(s->buf_size, MIN(max_bytes, op->bytes));
 350    assert(op->bytes);
 351    assert(op->bytes < BDRV_REQUEST_MAX_BYTES);
 352    *op->bytes_handled = op->bytes;
 353
 354    if (s->cow_bitmap) {
 355        *op->bytes_handled += mirror_cow_align(s, &op->offset, &op->bytes);
 356    }
 357    /* Cannot exceed BDRV_REQUEST_MAX_BYTES + INT_MAX */
 358    assert(*op->bytes_handled <= UINT_MAX);
 359    assert(op->bytes <= s->buf_size);
 360    /* The offset is granularity-aligned because:
 361     * 1) Caller passes in aligned values;
 362     * 2) mirror_cow_align is used only when target cluster is larger. */
 363    assert(QEMU_IS_ALIGNED(op->offset, s->granularity));
 364    /* The range is sector-aligned, since bdrv_getlength() rounds up. */
 365    assert(QEMU_IS_ALIGNED(op->bytes, BDRV_SECTOR_SIZE));
 366    nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
 367
 368    while (s->buf_free_count < nb_chunks) {
 369        trace_mirror_yield_in_flight(s, op->offset, s->in_flight);
 370        mirror_wait_for_free_in_flight_slot(s);
 371    }
 372
 373    /* Now make a QEMUIOVector taking enough granularity-sized chunks
 374     * from s->buf_free.
 375     */
 376    qemu_iovec_init(&op->qiov, nb_chunks);
 377    while (nb_chunks-- > 0) {
 378        MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
 379        size_t remaining = op->bytes - op->qiov.size;
 380
 381        QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
 382        s->buf_free_count--;
 383        qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
 384    }
 385
 386    /* Copy the dirty cluster.  */
 387    s->in_flight++;
 388    s->bytes_in_flight += op->bytes;
 389    op->is_in_flight = true;
 390    trace_mirror_one_iteration(s, op->offset, op->bytes);
 391
 392    ret = bdrv_co_preadv(s->mirror_top_bs->backing, op->offset, op->bytes,
 393                         &op->qiov, 0);
 394    mirror_read_complete(op, ret);
 395}
 396
 397static void coroutine_fn mirror_co_zero(void *opaque)
 398{
 399    MirrorOp *op = opaque;
 400    int ret;
 401
 402    op->s->in_flight++;
 403    op->s->bytes_in_flight += op->bytes;
 404    *op->bytes_handled = op->bytes;
 405    op->is_in_flight = true;
 406
 407    ret = blk_co_pwrite_zeroes(op->s->target, op->offset, op->bytes,
 408                               op->s->unmap ? BDRV_REQ_MAY_UNMAP : 0);
 409    mirror_write_complete(op, ret);
 410}
 411
 412static void coroutine_fn mirror_co_discard(void *opaque)
 413{
 414    MirrorOp *op = opaque;
 415    int ret;
 416
 417    op->s->in_flight++;
 418    op->s->bytes_in_flight += op->bytes;
 419    *op->bytes_handled = op->bytes;
 420    op->is_in_flight = true;
 421
 422    ret = blk_co_pdiscard(op->s->target, op->offset, op->bytes);
 423    mirror_write_complete(op, ret);
 424}
 425
 426static unsigned mirror_perform(MirrorBlockJob *s, int64_t offset,
 427                               unsigned bytes, MirrorMethod mirror_method)
 428{
 429    MirrorOp *op;
 430    Coroutine *co;
 431    int64_t bytes_handled = -1;
 432
 433    op = g_new(MirrorOp, 1);
 434    *op = (MirrorOp){
 435        .s              = s,
 436        .offset         = offset,
 437        .bytes          = bytes,
 438        .bytes_handled  = &bytes_handled,
 439    };
 440    qemu_co_queue_init(&op->waiting_requests);
 441
 442    switch (mirror_method) {
 443    case MIRROR_METHOD_COPY:
 444        co = qemu_coroutine_create(mirror_co_read, op);
 445        break;
 446    case MIRROR_METHOD_ZERO:
 447        co = qemu_coroutine_create(mirror_co_zero, op);
 448        break;
 449    case MIRROR_METHOD_DISCARD:
 450        co = qemu_coroutine_create(mirror_co_discard, op);
 451        break;
 452    default:
 453        abort();
 454    }
 455    op->co = co;
 456
 457    QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next);
 458    qemu_coroutine_enter(co);
 459    /* At this point, ownership of op has been moved to the coroutine
 460     * and the object may already be freed */
 461
 462    /* Assert that this value has been set */
 463    assert(bytes_handled >= 0);
 464
 465    /* Same assertion as in mirror_co_read() (and for mirror_co_read()
 466     * and mirror_co_discard(), bytes_handled == op->bytes, which
 467     * is the @bytes parameter given to this function) */
 468    assert(bytes_handled <= UINT_MAX);
 469    return bytes_handled;
 470}
 471
 472static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
 473{
 474    BlockDriverState *source = s->mirror_top_bs->backing->bs;
 475    MirrorOp *pseudo_op;
 476    int64_t offset;
 477    uint64_t delay_ns = 0, ret = 0;
 478    /* At least the first dirty chunk is mirrored in one iteration. */
 479    int nb_chunks = 1;
 480    bool write_zeroes_ok = bdrv_can_write_zeroes_with_unmap(blk_bs(s->target));
 481    int max_io_bytes = MAX(s->buf_size / MAX_IN_FLIGHT, MAX_IO_BYTES);
 482
 483    bdrv_dirty_bitmap_lock(s->dirty_bitmap);
 484    offset = bdrv_dirty_iter_next(s->dbi);
 485    if (offset < 0) {
 486        bdrv_set_dirty_iter(s->dbi, 0);
 487        offset = bdrv_dirty_iter_next(s->dbi);
 488        trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
 489        assert(offset >= 0);
 490    }
 491    bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
 492
 493    /*
 494     * Wait for concurrent requests to @offset.  The next loop will limit the
 495     * copied area based on in_flight_bitmap so we only copy an area that does
 496     * not overlap with concurrent in-flight requests.  Still, we would like to
 497     * copy something, so wait until there are at least no more requests to the
 498     * very beginning of the area.
 499     */
 500    mirror_wait_on_conflicts(NULL, s, offset, 1);
 501
 502    job_pause_point(&s->common.job);
 503
 504    /* Find the number of consective dirty chunks following the first dirty
 505     * one, and wait for in flight requests in them. */
 506    bdrv_dirty_bitmap_lock(s->dirty_bitmap);
 507    while (nb_chunks * s->granularity < s->buf_size) {
 508        int64_t next_dirty;
 509        int64_t next_offset = offset + nb_chunks * s->granularity;
 510        int64_t next_chunk = next_offset / s->granularity;
 511        if (next_offset >= s->bdev_length ||
 512            !bdrv_dirty_bitmap_get_locked(s->dirty_bitmap, next_offset)) {
 513            break;
 514        }
 515        if (test_bit(next_chunk, s->in_flight_bitmap)) {
 516            break;
 517        }
 518
 519        next_dirty = bdrv_dirty_iter_next(s->dbi);
 520        if (next_dirty > next_offset || next_dirty < 0) {
 521            /* The bitmap iterator's cache is stale, refresh it */
 522            bdrv_set_dirty_iter(s->dbi, next_offset);
 523            next_dirty = bdrv_dirty_iter_next(s->dbi);
 524        }
 525        assert(next_dirty == next_offset);
 526        nb_chunks++;
 527    }
 528
 529    /* Clear dirty bits before querying the block status, because
 530     * calling bdrv_block_status_above could yield - if some blocks are
 531     * marked dirty in this window, we need to know.
 532     */
 533    bdrv_reset_dirty_bitmap_locked(s->dirty_bitmap, offset,
 534                                   nb_chunks * s->granularity);
 535    bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
 536
 537    /* Before claiming an area in the in-flight bitmap, we have to
 538     * create a MirrorOp for it so that conflicting requests can wait
 539     * for it.  mirror_perform() will create the real MirrorOps later,
 540     * for now we just create a pseudo operation that will wake up all
 541     * conflicting requests once all real operations have been
 542     * launched. */
 543    pseudo_op = g_new(MirrorOp, 1);
 544    *pseudo_op = (MirrorOp){
 545        .offset         = offset,
 546        .bytes          = nb_chunks * s->granularity,
 547        .is_pseudo_op   = true,
 548    };
 549    qemu_co_queue_init(&pseudo_op->waiting_requests);
 550    QTAILQ_INSERT_TAIL(&s->ops_in_flight, pseudo_op, next);
 551
 552    bitmap_set(s->in_flight_bitmap, offset / s->granularity, nb_chunks);
 553    while (nb_chunks > 0 && offset < s->bdev_length) {
 554        int ret;
 555        int64_t io_bytes;
 556        int64_t io_bytes_acct;
 557        MirrorMethod mirror_method = MIRROR_METHOD_COPY;
 558
 559        assert(!(offset % s->granularity));
 560        ret = bdrv_block_status_above(source, NULL, offset,
 561                                      nb_chunks * s->granularity,
 562                                      &io_bytes, NULL, NULL);
 563        if (ret < 0) {
 564            io_bytes = MIN(nb_chunks * s->granularity, max_io_bytes);
 565        } else if (ret & BDRV_BLOCK_DATA) {
 566            io_bytes = MIN(io_bytes, max_io_bytes);
 567        }
 568
 569        io_bytes -= io_bytes % s->granularity;
 570        if (io_bytes < s->granularity) {
 571            io_bytes = s->granularity;
 572        } else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) {
 573            int64_t target_offset;
 574            int64_t target_bytes;
 575            bdrv_round_to_clusters(blk_bs(s->target), offset, io_bytes,
 576                                   &target_offset, &target_bytes);
 577            if (target_offset == offset &&
 578                target_bytes == io_bytes) {
 579                mirror_method = ret & BDRV_BLOCK_ZERO ?
 580                                    MIRROR_METHOD_ZERO :
 581                                    MIRROR_METHOD_DISCARD;
 582            }
 583        }
 584
 585        while (s->in_flight >= MAX_IN_FLIGHT) {
 586            trace_mirror_yield_in_flight(s, offset, s->in_flight);
 587            mirror_wait_for_free_in_flight_slot(s);
 588        }
 589
 590        if (s->ret < 0) {
 591            ret = 0;
 592            goto fail;
 593        }
 594
 595        io_bytes = mirror_clip_bytes(s, offset, io_bytes);
 596        io_bytes = mirror_perform(s, offset, io_bytes, mirror_method);
 597        if (mirror_method != MIRROR_METHOD_COPY && write_zeroes_ok) {
 598            io_bytes_acct = 0;
 599        } else {
 600            io_bytes_acct = io_bytes;
 601        }
 602        assert(io_bytes);
 603        offset += io_bytes;
 604        nb_chunks -= DIV_ROUND_UP(io_bytes, s->granularity);
 605        delay_ns = block_job_ratelimit_get_delay(&s->common, io_bytes_acct);
 606    }
 607
 608    ret = delay_ns;
 609fail:
 610    QTAILQ_REMOVE(&s->ops_in_flight, pseudo_op, next);
 611    qemu_co_queue_restart_all(&pseudo_op->waiting_requests);
 612    g_free(pseudo_op);
 613
 614    return ret;
 615}
 616
 617static void mirror_free_init(MirrorBlockJob *s)
 618{
 619    int granularity = s->granularity;
 620    size_t buf_size = s->buf_size;
 621    uint8_t *buf = s->buf;
 622
 623    assert(s->buf_free_count == 0);
 624    QSIMPLEQ_INIT(&s->buf_free);
 625    while (buf_size != 0) {
 626        MirrorBuffer *cur = (MirrorBuffer *)buf;
 627        QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
 628        s->buf_free_count++;
 629        buf_size -= granularity;
 630        buf += granularity;
 631    }
 632}
 633
 634/* This is also used for the .pause callback. There is no matching
 635 * mirror_resume() because mirror_run() will begin iterating again
 636 * when the job is resumed.
 637 */
 638static void coroutine_fn mirror_wait_for_all_io(MirrorBlockJob *s)
 639{
 640    while (s->in_flight > 0) {
 641        mirror_wait_for_free_in_flight_slot(s);
 642    }
 643}
 644
 645/**
 646 * mirror_exit_common: handle both abort() and prepare() cases.
 647 * for .prepare, returns 0 on success and -errno on failure.
 648 * for .abort cases, denoted by abort = true, MUST return 0.
 649 */
 650static int mirror_exit_common(Job *job)
 651{
 652    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
 653    BlockJob *bjob = &s->common;
 654    MirrorBDSOpaque *bs_opaque;
 655    AioContext *replace_aio_context = NULL;
 656    BlockDriverState *src;
 657    BlockDriverState *target_bs;
 658    BlockDriverState *mirror_top_bs;
 659    Error *local_err = NULL;
 660    bool abort = job->ret < 0;
 661    int ret = 0;
 662
 663    if (s->prepared) {
 664        return 0;
 665    }
 666    s->prepared = true;
 667
 668    mirror_top_bs = s->mirror_top_bs;
 669    bs_opaque = mirror_top_bs->opaque;
 670    src = mirror_top_bs->backing->bs;
 671    target_bs = blk_bs(s->target);
 672
 673    if (bdrv_chain_contains(src, target_bs)) {
 674        bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs);
 675    }
 676
 677    bdrv_release_dirty_bitmap(s->dirty_bitmap);
 678
 679    /* Make sure that the source BDS doesn't go away during bdrv_replace_node,
 680     * before we can call bdrv_drained_end */
 681    bdrv_ref(src);
 682    bdrv_ref(mirror_top_bs);
 683    bdrv_ref(target_bs);
 684
 685    /*
 686     * Remove target parent that still uses BLK_PERM_WRITE/RESIZE before
 687     * inserting target_bs at s->to_replace, where we might not be able to get
 688     * these permissions.
 689     */
 690    blk_unref(s->target);
 691    s->target = NULL;
 692
 693    /* We don't access the source any more. Dropping any WRITE/RESIZE is
 694     * required before it could become a backing file of target_bs. Not having
 695     * these permissions any more means that we can't allow any new requests on
 696     * mirror_top_bs from now on, so keep it drained. */
 697    bdrv_drained_begin(mirror_top_bs);
 698    bs_opaque->stop = true;
 699    bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
 700                             &error_abort);
 701    if (!abort && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
 702        BlockDriverState *backing = s->is_none_mode ? src : s->base;
 703        BlockDriverState *unfiltered_target = bdrv_skip_filters(target_bs);
 704
 705        if (bdrv_cow_bs(unfiltered_target) != backing) {
 706            bdrv_set_backing_hd(unfiltered_target, backing, &local_err);
 707            if (local_err) {
 708                error_report_err(local_err);
 709                local_err = NULL;
 710                ret = -EPERM;
 711            }
 712        }
 713    } else if (!abort && s->backing_mode == MIRROR_OPEN_BACKING_CHAIN) {
 714        assert(!bdrv_backing_chain_next(target_bs));
 715        ret = bdrv_open_backing_file(bdrv_skip_filters(target_bs), NULL,
 716                                     "backing", &local_err);
 717        if (ret < 0) {
 718            error_report_err(local_err);
 719            local_err = NULL;
 720        }
 721    }
 722
 723    if (s->to_replace) {
 724        replace_aio_context = bdrv_get_aio_context(s->to_replace);
 725        aio_context_acquire(replace_aio_context);
 726    }
 727
 728    if (s->should_complete && !abort) {
 729        BlockDriverState *to_replace = s->to_replace ?: src;
 730        bool ro = bdrv_is_read_only(to_replace);
 731
 732        if (ro != bdrv_is_read_only(target_bs)) {
 733            bdrv_reopen_set_read_only(target_bs, ro, NULL);
 734        }
 735
 736        /* The mirror job has no requests in flight any more, but we need to
 737         * drain potential other users of the BDS before changing the graph. */
 738        assert(s->in_drain);
 739        bdrv_drained_begin(target_bs);
 740        /*
 741         * Cannot use check_to_replace_node() here, because that would
 742         * check for an op blocker on @to_replace, and we have our own
 743         * there.
 744         */
 745        if (bdrv_recurse_can_replace(src, to_replace)) {
 746            bdrv_replace_node(to_replace, target_bs, &local_err);
 747        } else {
 748            error_setg(&local_err, "Can no longer replace '%s' by '%s', "
 749                       "because it can no longer be guaranteed that doing so "
 750                       "would not lead to an abrupt change of visible data",
 751                       to_replace->node_name, target_bs->node_name);
 752        }
 753        bdrv_drained_end(target_bs);
 754        if (local_err) {
 755            error_report_err(local_err);
 756            ret = -EPERM;
 757        }
 758    }
 759    if (s->to_replace) {
 760        bdrv_op_unblock_all(s->to_replace, s->replace_blocker);
 761        error_free(s->replace_blocker);
 762        bdrv_unref(s->to_replace);
 763    }
 764    if (replace_aio_context) {
 765        aio_context_release(replace_aio_context);
 766    }
 767    g_free(s->replaces);
 768    bdrv_unref(target_bs);
 769
 770    /*
 771     * Remove the mirror filter driver from the graph. Before this, get rid of
 772     * the blockers on the intermediate nodes so that the resulting state is
 773     * valid.
 774     */
 775    block_job_remove_all_bdrv(bjob);
 776    bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
 777
 778    bs_opaque->job = NULL;
 779
 780    bdrv_drained_end(src);
 781    bdrv_drained_end(mirror_top_bs);
 782    s->in_drain = false;
 783    bdrv_unref(mirror_top_bs);
 784    bdrv_unref(src);
 785
 786    return ret;
 787}
 788
 789static int mirror_prepare(Job *job)
 790{
 791    return mirror_exit_common(job);
 792}
 793
 794static void mirror_abort(Job *job)
 795{
 796    int ret = mirror_exit_common(job);
 797    assert(ret == 0);
 798}
 799
 800static void coroutine_fn mirror_throttle(MirrorBlockJob *s)
 801{
 802    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 803
 804    if (now - s->last_pause_ns > BLOCK_JOB_SLICE_TIME) {
 805        s->last_pause_ns = now;
 806        job_sleep_ns(&s->common.job, 0);
 807    } else {
 808        job_pause_point(&s->common.job);
 809    }
 810}
 811
 812static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
 813{
 814    int64_t offset;
 815    BlockDriverState *bs = s->mirror_top_bs->backing->bs;
 816    BlockDriverState *target_bs = blk_bs(s->target);
 817    int ret;
 818    int64_t count;
 819
 820    if (s->zero_target) {
 821        if (!bdrv_can_write_zeroes_with_unmap(target_bs)) {
 822            bdrv_set_dirty_bitmap(s->dirty_bitmap, 0, s->bdev_length);
 823            return 0;
 824        }
 825
 826        s->initial_zeroing_ongoing = true;
 827        for (offset = 0; offset < s->bdev_length; ) {
 828            int bytes = MIN(s->bdev_length - offset,
 829                            QEMU_ALIGN_DOWN(INT_MAX, s->granularity));
 830
 831            mirror_throttle(s);
 832
 833            if (job_is_cancelled(&s->common.job)) {
 834                s->initial_zeroing_ongoing = false;
 835                return 0;
 836            }
 837
 838            if (s->in_flight >= MAX_IN_FLIGHT) {
 839                trace_mirror_yield(s, UINT64_MAX, s->buf_free_count,
 840                                   s->in_flight);
 841                mirror_wait_for_free_in_flight_slot(s);
 842                continue;
 843            }
 844
 845            mirror_perform(s, offset, bytes, MIRROR_METHOD_ZERO);
 846            offset += bytes;
 847        }
 848
 849        mirror_wait_for_all_io(s);
 850        s->initial_zeroing_ongoing = false;
 851    }
 852
 853    /* First part, loop on the sectors and initialize the dirty bitmap.  */
 854    for (offset = 0; offset < s->bdev_length; ) {
 855        /* Just to make sure we are not exceeding int limit. */
 856        int bytes = MIN(s->bdev_length - offset,
 857                        QEMU_ALIGN_DOWN(INT_MAX, s->granularity));
 858
 859        mirror_throttle(s);
 860
 861        if (job_is_cancelled(&s->common.job)) {
 862            return 0;
 863        }
 864
 865        ret = bdrv_is_allocated_above(bs, s->base_overlay, true, offset, bytes,
 866                                      &count);
 867        if (ret < 0) {
 868            return ret;
 869        }
 870
 871        assert(count);
 872        if (ret > 0) {
 873            bdrv_set_dirty_bitmap(s->dirty_bitmap, offset, count);
 874        }
 875        offset += count;
 876    }
 877    return 0;
 878}
 879
 880/* Called when going out of the streaming phase to flush the bulk of the
 881 * data to the medium, or just before completing.
 882 */
 883static int mirror_flush(MirrorBlockJob *s)
 884{
 885    int ret = blk_flush(s->target);
 886    if (ret < 0) {
 887        if (mirror_error_action(s, false, -ret) == BLOCK_ERROR_ACTION_REPORT) {
 888            s->ret = ret;
 889        }
 890    }
 891    return ret;
 892}
 893
 894static int coroutine_fn mirror_run(Job *job, Error **errp)
 895{
 896    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
 897    BlockDriverState *bs = s->mirror_top_bs->backing->bs;
 898    BlockDriverState *target_bs = blk_bs(s->target);
 899    bool need_drain = true;
 900    BlockDeviceIoStatus iostatus;
 901    int64_t length;
 902    int64_t target_length;
 903    BlockDriverInfo bdi;
 904    char backing_filename[2]; /* we only need 2 characters because we are only
 905                                 checking for a NULL string */
 906    int ret = 0;
 907
 908    if (job_is_cancelled(&s->common.job)) {
 909        goto immediate_exit;
 910    }
 911
 912    s->bdev_length = bdrv_getlength(bs);
 913    if (s->bdev_length < 0) {
 914        ret = s->bdev_length;
 915        goto immediate_exit;
 916    }
 917
 918    target_length = blk_getlength(s->target);
 919    if (target_length < 0) {
 920        ret = target_length;
 921        goto immediate_exit;
 922    }
 923
 924    /* Active commit must resize the base image if its size differs from the
 925     * active layer. */
 926    if (s->base == blk_bs(s->target)) {
 927        if (s->bdev_length > target_length) {
 928            ret = blk_co_truncate(s->target, s->bdev_length, false,
 929                                  PREALLOC_MODE_OFF, 0, NULL);
 930            if (ret < 0) {
 931                goto immediate_exit;
 932            }
 933        }
 934    } else if (s->bdev_length != target_length) {
 935        error_setg(errp, "Source and target image have different sizes");
 936        ret = -EINVAL;
 937        goto immediate_exit;
 938    }
 939
 940    if (s->bdev_length == 0) {
 941        /* Transition to the READY state and wait for complete. */
 942        job_transition_to_ready(&s->common.job);
 943        s->actively_synced = true;
 944        while (!job_cancel_requested(&s->common.job) && !s->should_complete) {
 945            job_yield(&s->common.job);
 946        }
 947        goto immediate_exit;
 948    }
 949
 950    length = DIV_ROUND_UP(s->bdev_length, s->granularity);
 951    s->in_flight_bitmap = bitmap_new(length);
 952
 953    /* If we have no backing file yet in the destination, we cannot let
 954     * the destination do COW.  Instead, we copy sectors around the
 955     * dirty data if needed.  We need a bitmap to do that.
 956     */
 957    bdrv_get_backing_filename(target_bs, backing_filename,
 958                              sizeof(backing_filename));
 959    if (!bdrv_get_info(target_bs, &bdi) && bdi.cluster_size) {
 960        s->target_cluster_size = bdi.cluster_size;
 961    } else {
 962        s->target_cluster_size = BDRV_SECTOR_SIZE;
 963    }
 964    if (backing_filename[0] && !bdrv_backing_chain_next(target_bs) &&
 965        s->granularity < s->target_cluster_size) {
 966        s->buf_size = MAX(s->buf_size, s->target_cluster_size);
 967        s->cow_bitmap = bitmap_new(length);
 968    }
 969    s->max_iov = MIN(bs->bl.max_iov, target_bs->bl.max_iov);
 970
 971    s->buf = qemu_try_blockalign(bs, s->buf_size);
 972    if (s->buf == NULL) {
 973        ret = -ENOMEM;
 974        goto immediate_exit;
 975    }
 976
 977    mirror_free_init(s);
 978
 979    s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
 980    if (!s->is_none_mode) {
 981        ret = mirror_dirty_init(s);
 982        if (ret < 0 || job_is_cancelled(&s->common.job)) {
 983            goto immediate_exit;
 984        }
 985    }
 986
 987    assert(!s->dbi);
 988    s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap);
 989    for (;;) {
 990        uint64_t delay_ns = 0;
 991        int64_t cnt, delta;
 992        bool should_complete;
 993
 994        if (s->ret < 0) {
 995            ret = s->ret;
 996            goto immediate_exit;
 997        }
 998
 999        job_pause_point(&s->common.job);
1000
1001        if (job_is_cancelled(&s->common.job)) {
1002            ret = 0;
1003            goto immediate_exit;
1004        }
1005
1006        cnt = bdrv_get_dirty_count(s->dirty_bitmap);
1007        /* cnt is the number of dirty bytes remaining and s->bytes_in_flight is
1008         * the number of bytes currently being processed; together those are
1009         * the current remaining operation length */
1010        job_progress_set_remaining(&s->common.job,
1011                                   s->bytes_in_flight + cnt +
1012                                   s->active_write_bytes_in_flight);
1013
1014        /* Note that even when no rate limit is applied we need to yield
1015         * periodically with no pending I/O so that bdrv_drain_all() returns.
1016         * We do so every BLKOCK_JOB_SLICE_TIME nanoseconds, or when there is
1017         * an error, or when the source is clean, whichever comes first. */
1018        delta = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - s->last_pause_ns;
1019        WITH_JOB_LOCK_GUARD() {
1020            iostatus = s->common.iostatus;
1021        }
1022        if (delta < BLOCK_JOB_SLICE_TIME &&
1023            iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
1024            if (s->in_flight >= MAX_IN_FLIGHT || s->buf_free_count == 0 ||
1025                (cnt == 0 && s->in_flight > 0)) {
1026                trace_mirror_yield(s, cnt, s->buf_free_count, s->in_flight);
1027                mirror_wait_for_free_in_flight_slot(s);
1028                continue;
1029            } else if (cnt != 0) {
1030                delay_ns = mirror_iteration(s);
1031            }
1032        }
1033
1034        should_complete = false;
1035        if (s->in_flight == 0 && cnt == 0) {
1036            trace_mirror_before_flush(s);
1037            if (!job_is_ready(&s->common.job)) {
1038                if (mirror_flush(s) < 0) {
1039                    /* Go check s->ret.  */
1040                    continue;
1041                }
1042                /* We're out of the streaming phase.  From now on, if the job
1043                 * is cancelled we will actually complete all pending I/O and
1044                 * report completion.  This way, block-job-cancel will leave
1045                 * the target in a consistent state.
1046                 */
1047                job_transition_to_ready(&s->common.job);
1048                if (s->copy_mode != MIRROR_COPY_MODE_BACKGROUND) {
1049                    s->actively_synced = true;
1050                }
1051            }
1052
1053            should_complete = s->should_complete ||
1054                job_cancel_requested(&s->common.job);
1055            cnt = bdrv_get_dirty_count(s->dirty_bitmap);
1056        }
1057
1058        if (cnt == 0 && should_complete) {
1059            /* The dirty bitmap is not updated while operations are pending.
1060             * If we're about to exit, wait for pending operations before
1061             * calling bdrv_get_dirty_count(bs), or we may exit while the
1062             * source has dirty data to copy!
1063             *
1064             * Note that I/O can be submitted by the guest while
1065             * mirror_populate runs, so pause it now.  Before deciding
1066             * whether to switch to target check one last time if I/O has
1067             * come in the meanwhile, and if not flush the data to disk.
1068             */
1069            trace_mirror_before_drain(s, cnt);
1070
1071            s->in_drain = true;
1072            bdrv_drained_begin(bs);
1073
1074            /* Must be zero because we are drained */
1075            assert(s->in_active_write_counter == 0);
1076
1077            cnt = bdrv_get_dirty_count(s->dirty_bitmap);
1078            if (cnt > 0 || mirror_flush(s) < 0) {
1079                bdrv_drained_end(bs);
1080                s->in_drain = false;
1081                continue;
1082            }
1083
1084            /* The two disks are in sync.  Exit and report successful
1085             * completion.
1086             */
1087            assert(QLIST_EMPTY(&bs->tracked_requests));
1088            need_drain = false;
1089            break;
1090        }
1091
1092        if (job_is_ready(&s->common.job) && !should_complete) {
1093            delay_ns = (s->in_flight == 0 &&
1094                        cnt == 0 ? BLOCK_JOB_SLICE_TIME : 0);
1095        }
1096        trace_mirror_before_sleep(s, cnt, job_is_ready(&s->common.job),
1097                                  delay_ns);
1098        job_sleep_ns(&s->common.job, delay_ns);
1099        s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
1100    }
1101
1102immediate_exit:
1103    if (s->in_flight > 0) {
1104        /* We get here only if something went wrong.  Either the job failed,
1105         * or it was cancelled prematurely so that we do not guarantee that
1106         * the target is a copy of the source.
1107         */
1108        assert(ret < 0 || job_is_cancelled(&s->common.job));
1109        assert(need_drain);
1110        mirror_wait_for_all_io(s);
1111    }
1112
1113    assert(s->in_flight == 0);
1114    qemu_vfree(s->buf);
1115    g_free(s->cow_bitmap);
1116    g_free(s->in_flight_bitmap);
1117    bdrv_dirty_iter_free(s->dbi);
1118
1119    if (need_drain) {
1120        s->in_drain = true;
1121        bdrv_drained_begin(bs);
1122    }
1123
1124    return ret;
1125}
1126
1127static void mirror_complete(Job *job, Error **errp)
1128{
1129    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
1130
1131    if (!job_is_ready(job)) {
1132        error_setg(errp, "The active block job '%s' cannot be completed",
1133                   job->id);
1134        return;
1135    }
1136
1137    /* block all operations on to_replace bs */
1138    if (s->replaces) {
1139        AioContext *replace_aio_context;
1140
1141        s->to_replace = bdrv_find_node(s->replaces);
1142        if (!s->to_replace) {
1143            error_setg(errp, "Node name '%s' not found", s->replaces);
1144            return;
1145        }
1146
1147        replace_aio_context = bdrv_get_aio_context(s->to_replace);
1148        aio_context_acquire(replace_aio_context);
1149
1150        /* TODO Translate this into child freeze system. */
1151        error_setg(&s->replace_blocker,
1152                   "block device is in use by block-job-complete");
1153        bdrv_op_block_all(s->to_replace, s->replace_blocker);
1154        bdrv_ref(s->to_replace);
1155
1156        aio_context_release(replace_aio_context);
1157    }
1158
1159    s->should_complete = true;
1160
1161    /* If the job is paused, it will be re-entered when it is resumed */
1162    WITH_JOB_LOCK_GUARD() {
1163        if (!job->paused) {
1164            job_enter_cond_locked(job, NULL);
1165        }
1166    }
1167}
1168
1169static void coroutine_fn mirror_pause(Job *job)
1170{
1171    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
1172
1173    mirror_wait_for_all_io(s);
1174}
1175
1176static bool mirror_drained_poll(BlockJob *job)
1177{
1178    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
1179
1180    /* If the job isn't paused nor cancelled, we can't be sure that it won't
1181     * issue more requests. We make an exception if we've reached this point
1182     * from one of our own drain sections, to avoid a deadlock waiting for
1183     * ourselves.
1184     */
1185    WITH_JOB_LOCK_GUARD() {
1186        if (!s->common.job.paused && !job_is_cancelled_locked(&job->job)
1187            && !s->in_drain) {
1188            return true;
1189        }
1190    }
1191
1192    return !!s->in_flight;
1193}
1194
1195static bool mirror_cancel(Job *job, bool force)
1196{
1197    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
1198    BlockDriverState *target = blk_bs(s->target);
1199
1200    /*
1201     * Before the job is READY, we treat any cancellation like a
1202     * force-cancellation.
1203     */
1204    force = force || !job_is_ready(job);
1205
1206    if (force) {
1207        bdrv_cancel_in_flight(target);
1208    }
1209    return force;
1210}
1211
1212static bool commit_active_cancel(Job *job, bool force)
1213{
1214    /* Same as above in mirror_cancel() */
1215    return force || !job_is_ready(job);
1216}
1217
1218static const BlockJobDriver mirror_job_driver = {
1219    .job_driver = {
1220        .instance_size          = sizeof(MirrorBlockJob),
1221        .job_type               = JOB_TYPE_MIRROR,
1222        .free                   = block_job_free,
1223        .user_resume            = block_job_user_resume,
1224        .run                    = mirror_run,
1225        .prepare                = mirror_prepare,
1226        .abort                  = mirror_abort,
1227        .pause                  = mirror_pause,
1228        .complete               = mirror_complete,
1229        .cancel                 = mirror_cancel,
1230    },
1231    .drained_poll           = mirror_drained_poll,
1232};
1233
1234static const BlockJobDriver commit_active_job_driver = {
1235    .job_driver = {
1236        .instance_size          = sizeof(MirrorBlockJob),
1237        .job_type               = JOB_TYPE_COMMIT,
1238        .free                   = block_job_free,
1239        .user_resume            = block_job_user_resume,
1240        .run                    = mirror_run,
1241        .prepare                = mirror_prepare,
1242        .abort                  = mirror_abort,
1243        .pause                  = mirror_pause,
1244        .complete               = mirror_complete,
1245        .cancel                 = commit_active_cancel,
1246    },
1247    .drained_poll           = mirror_drained_poll,
1248};
1249
1250static void coroutine_fn
1251do_sync_target_write(MirrorBlockJob *job, MirrorMethod method,
1252                     uint64_t offset, uint64_t bytes,
1253                     QEMUIOVector *qiov, int flags)
1254{
1255    int ret;
1256    size_t qiov_offset = 0;
1257    int64_t bitmap_offset, bitmap_end;
1258
1259    if (!QEMU_IS_ALIGNED(offset, job->granularity) &&
1260        bdrv_dirty_bitmap_get(job->dirty_bitmap, offset))
1261    {
1262            /*
1263             * Dirty unaligned padding: ignore it.
1264             *
1265             * Reasoning:
1266             * 1. If we copy it, we can't reset corresponding bit in
1267             *    dirty_bitmap as there may be some "dirty" bytes still not
1268             *    copied.
1269             * 2. It's already dirty, so skipping it we don't diverge mirror
1270             *    progress.
1271             *
1272             * Note, that because of this, guest write may have no contribution
1273             * into mirror converge, but that's not bad, as we have background
1274             * process of mirroring. If under some bad circumstances (high guest
1275             * IO load) background process starve, we will not converge anyway,
1276             * even if each write will contribute, as guest is not guaranteed to
1277             * rewrite the whole disk.
1278             */
1279            qiov_offset = QEMU_ALIGN_UP(offset, job->granularity) - offset;
1280            if (bytes <= qiov_offset) {
1281                /* nothing to do after shrink */
1282                return;
1283            }
1284            offset += qiov_offset;
1285            bytes -= qiov_offset;
1286    }
1287
1288    if (!QEMU_IS_ALIGNED(offset + bytes, job->granularity) &&
1289        bdrv_dirty_bitmap_get(job->dirty_bitmap, offset + bytes - 1))
1290    {
1291        uint64_t tail = (offset + bytes) % job->granularity;
1292
1293        if (bytes <= tail) {
1294            /* nothing to do after shrink */
1295            return;
1296        }
1297        bytes -= tail;
1298    }
1299
1300    /*
1301     * Tails are either clean or shrunk, so for bitmap resetting
1302     * we safely align the range down.
1303     */
1304    bitmap_offset = QEMU_ALIGN_UP(offset, job->granularity);
1305    bitmap_end = QEMU_ALIGN_DOWN(offset + bytes, job->granularity);
1306    if (bitmap_offset < bitmap_end) {
1307        bdrv_reset_dirty_bitmap(job->dirty_bitmap, bitmap_offset,
1308                                bitmap_end - bitmap_offset);
1309    }
1310
1311    job_progress_increase_remaining(&job->common.job, bytes);
1312    job->active_write_bytes_in_flight += bytes;
1313
1314    switch (method) {
1315    case MIRROR_METHOD_COPY:
1316        ret = blk_co_pwritev_part(job->target, offset, bytes,
1317                                  qiov, qiov_offset, flags);
1318        break;
1319
1320    case MIRROR_METHOD_ZERO:
1321        assert(!qiov);
1322        ret = blk_co_pwrite_zeroes(job->target, offset, bytes, flags);
1323        break;
1324
1325    case MIRROR_METHOD_DISCARD:
1326        assert(!qiov);
1327        ret = blk_co_pdiscard(job->target, offset, bytes);
1328        break;
1329
1330    default:
1331        abort();
1332    }
1333
1334    job->active_write_bytes_in_flight -= bytes;
1335    if (ret >= 0) {
1336        job_progress_update(&job->common.job, bytes);
1337    } else {
1338        BlockErrorAction action;
1339
1340        /*
1341         * We failed, so we should mark dirty the whole area, aligned up.
1342         * Note that we don't care about shrunk tails if any: they were dirty
1343         * at function start, and they must be still dirty, as we've locked
1344         * the region for in-flight op.
1345         */
1346        bitmap_offset = QEMU_ALIGN_DOWN(offset, job->granularity);
1347        bitmap_end = QEMU_ALIGN_UP(offset + bytes, job->granularity);
1348        bdrv_set_dirty_bitmap(job->dirty_bitmap, bitmap_offset,
1349                              bitmap_end - bitmap_offset);
1350        job->actively_synced = false;
1351
1352        action = mirror_error_action(job, false, -ret);
1353        if (action == BLOCK_ERROR_ACTION_REPORT) {
1354            if (!job->ret) {
1355                job->ret = ret;
1356            }
1357        }
1358    }
1359}
1360
1361static MirrorOp *coroutine_fn active_write_prepare(MirrorBlockJob *s,
1362                                                   uint64_t offset,
1363                                                   uint64_t bytes)
1364{
1365    MirrorOp *op;
1366    uint64_t start_chunk = offset / s->granularity;
1367    uint64_t end_chunk = DIV_ROUND_UP(offset + bytes, s->granularity);
1368
1369    op = g_new(MirrorOp, 1);
1370    *op = (MirrorOp){
1371        .s                  = s,
1372        .offset             = offset,
1373        .bytes              = bytes,
1374        .is_active_write    = true,
1375        .is_in_flight       = true,
1376        .co                 = qemu_coroutine_self(),
1377    };
1378    qemu_co_queue_init(&op->waiting_requests);
1379    QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next);
1380
1381    s->in_active_write_counter++;
1382
1383    /*
1384     * Wait for concurrent requests affecting the area.  If there are already
1385     * running requests that are copying off now-to-be stale data in the area,
1386     * we must wait for them to finish before we begin writing fresh data to the
1387     * target so that the write operations appear in the correct order.
1388     * Note that background requests (see mirror_iteration()) in contrast only
1389     * wait for conflicting requests at the start of the dirty area, and then
1390     * (based on the in_flight_bitmap) truncate the area to copy so it will not
1391     * conflict with any requests beyond that.  For active writes, however, we
1392     * cannot truncate that area.  The request from our parent must be blocked
1393     * until the area is copied in full.  Therefore, we must wait for the whole
1394     * area to become free of concurrent requests.
1395     */
1396    mirror_wait_on_conflicts(op, s, offset, bytes);
1397
1398    bitmap_set(s->in_flight_bitmap, start_chunk, end_chunk - start_chunk);
1399
1400    return op;
1401}
1402
1403static void coroutine_fn active_write_settle(MirrorOp *op)
1404{
1405    uint64_t start_chunk = op->offset / op->s->granularity;
1406    uint64_t end_chunk = DIV_ROUND_UP(op->offset + op->bytes,
1407                                      op->s->granularity);
1408
1409    if (!--op->s->in_active_write_counter && op->s->actively_synced) {
1410        BdrvChild *source = op->s->mirror_top_bs->backing;
1411
1412        if (QLIST_FIRST(&source->bs->parents) == source &&
1413            QLIST_NEXT(source, next_parent) == NULL)
1414        {
1415            /* Assert that we are back in sync once all active write
1416             * operations are settled.
1417             * Note that we can only assert this if the mirror node
1418             * is the source node's only parent. */
1419            assert(!bdrv_get_dirty_count(op->s->dirty_bitmap));
1420        }
1421    }
1422    bitmap_clear(op->s->in_flight_bitmap, start_chunk, end_chunk - start_chunk);
1423    QTAILQ_REMOVE(&op->s->ops_in_flight, op, next);
1424    qemu_co_queue_restart_all(&op->waiting_requests);
1425    g_free(op);
1426}
1427
1428static int coroutine_fn bdrv_mirror_top_preadv(BlockDriverState *bs,
1429    int64_t offset, int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags)
1430{
1431    return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
1432}
1433
1434static int coroutine_fn bdrv_mirror_top_do_write(BlockDriverState *bs,
1435    MirrorMethod method, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov,
1436    int flags)
1437{
1438    MirrorOp *op = NULL;
1439    MirrorBDSOpaque *s = bs->opaque;
1440    int ret = 0;
1441    bool copy_to_target = false;
1442
1443    if (s->job) {
1444        copy_to_target = s->job->ret >= 0 &&
1445                         !job_is_cancelled(&s->job->common.job) &&
1446                         s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
1447    }
1448
1449    if (copy_to_target) {
1450        op = active_write_prepare(s->job, offset, bytes);
1451    }
1452
1453    switch (method) {
1454    case MIRROR_METHOD_COPY:
1455        ret = bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
1456        break;
1457
1458    case MIRROR_METHOD_ZERO:
1459        ret = bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
1460        break;
1461
1462    case MIRROR_METHOD_DISCARD:
1463        ret = bdrv_co_pdiscard(bs->backing, offset, bytes);
1464        break;
1465
1466    default:
1467        abort();
1468    }
1469
1470    if (ret < 0) {
1471        goto out;
1472    }
1473
1474    if (copy_to_target) {
1475        do_sync_target_write(s->job, method, offset, bytes, qiov, flags);
1476    }
1477
1478out:
1479    if (copy_to_target) {
1480        active_write_settle(op);
1481    }
1482    return ret;
1483}
1484
1485static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
1486    int64_t offset, int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags)
1487{
1488    MirrorBDSOpaque *s = bs->opaque;
1489    QEMUIOVector bounce_qiov;
1490    void *bounce_buf;
1491    int ret = 0;
1492    bool copy_to_target = false;
1493
1494    if (s->job) {
1495        copy_to_target = s->job->ret >= 0 &&
1496                         !job_is_cancelled(&s->job->common.job) &&
1497                         s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
1498    }
1499
1500    if (copy_to_target) {
1501        /* The guest might concurrently modify the data to write; but
1502         * the data on source and destination must match, so we have
1503         * to use a bounce buffer if we are going to write to the
1504         * target now. */
1505        bounce_buf = qemu_blockalign(bs, bytes);
1506        iov_to_buf_full(qiov->iov, qiov->niov, 0, bounce_buf, bytes);
1507
1508        qemu_iovec_init(&bounce_qiov, 1);
1509        qemu_iovec_add(&bounce_qiov, bounce_buf, bytes);
1510        qiov = &bounce_qiov;
1511
1512        flags &= ~BDRV_REQ_REGISTERED_BUF;
1513    }
1514
1515    ret = bdrv_mirror_top_do_write(bs, MIRROR_METHOD_COPY, offset, bytes, qiov,
1516                                   flags);
1517
1518    if (copy_to_target) {
1519        qemu_iovec_destroy(&bounce_qiov);
1520        qemu_vfree(bounce_buf);
1521    }
1522
1523    return ret;
1524}
1525
1526static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
1527{
1528    if (bs->backing == NULL) {
1529        /* we can be here after failed bdrv_append in mirror_start_job */
1530        return 0;
1531    }
1532    return bdrv_co_flush(bs->backing->bs);
1533}
1534
1535static int coroutine_fn bdrv_mirror_top_pwrite_zeroes(BlockDriverState *bs,
1536    int64_t offset, int64_t bytes, BdrvRequestFlags flags)
1537{
1538    return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_ZERO, offset, bytes, NULL,
1539                                    flags);
1540}
1541
1542static int coroutine_fn bdrv_mirror_top_pdiscard(BlockDriverState *bs,
1543    int64_t offset, int64_t bytes)
1544{
1545    return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_DISCARD, offset, bytes,
1546                                    NULL, 0);
1547}
1548
1549static void bdrv_mirror_top_refresh_filename(BlockDriverState *bs)
1550{
1551    if (bs->backing == NULL) {
1552        /* we can be here after failed bdrv_attach_child in
1553         * bdrv_set_backing_hd */
1554        return;
1555    }
1556    pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
1557            bs->backing->bs->filename);
1558}
1559
1560static void bdrv_mirror_top_child_perm(BlockDriverState *bs, BdrvChild *c,
1561                                       BdrvChildRole role,
1562                                       BlockReopenQueue *reopen_queue,
1563                                       uint64_t perm, uint64_t shared,
1564                                       uint64_t *nperm, uint64_t *nshared)
1565{
1566    MirrorBDSOpaque *s = bs->opaque;
1567
1568    if (s->stop) {
1569        /*
1570         * If the job is to be stopped, we do not need to forward
1571         * anything to the real image.
1572         */
1573        *nperm = 0;
1574        *nshared = BLK_PERM_ALL;
1575        return;
1576    }
1577
1578    bdrv_default_perms(bs, c, role, reopen_queue,
1579                       perm, shared, nperm, nshared);
1580
1581    if (s->is_commit) {
1582        /*
1583         * For commit jobs, we cannot take CONSISTENT_READ, because
1584         * that permission is unshared for everything above the base
1585         * node (except for filters on the base node).
1586         * We also have to force-share the WRITE permission, or
1587         * otherwise we would block ourselves at the base node (if
1588         * writes are blocked for a node, they are also blocked for
1589         * its backing file).
1590         * (We could also share RESIZE, because it may be needed for
1591         * the target if its size is less than the top node's; but
1592         * bdrv_default_perms_for_cow() automatically shares RESIZE
1593         * for backing nodes if WRITE is shared, so there is no need
1594         * to do it here.)
1595         */
1596        *nperm &= ~BLK_PERM_CONSISTENT_READ;
1597        *nshared |= BLK_PERM_WRITE;
1598    }
1599}
1600
1601/* Dummy node that provides consistent read to its users without requiring it
1602 * from its backing file and that allows writes on the backing file chain. */
1603static BlockDriver bdrv_mirror_top = {
1604    .format_name                = "mirror_top",
1605    .bdrv_co_preadv             = bdrv_mirror_top_preadv,
1606    .bdrv_co_pwritev            = bdrv_mirror_top_pwritev,
1607    .bdrv_co_pwrite_zeroes      = bdrv_mirror_top_pwrite_zeroes,
1608    .bdrv_co_pdiscard           = bdrv_mirror_top_pdiscard,
1609    .bdrv_co_flush              = bdrv_mirror_top_flush,
1610    .bdrv_refresh_filename      = bdrv_mirror_top_refresh_filename,
1611    .bdrv_child_perm            = bdrv_mirror_top_child_perm,
1612
1613    .is_filter                  = true,
1614    .filtered_child_is_backing  = true,
1615};
1616
1617static BlockJob *mirror_start_job(
1618                             const char *job_id, BlockDriverState *bs,
1619                             int creation_flags, BlockDriverState *target,
1620                             const char *replaces, int64_t speed,
1621                             uint32_t granularity, int64_t buf_size,
1622                             BlockMirrorBackingMode backing_mode,
1623                             bool zero_target,
1624                             BlockdevOnError on_source_error,
1625                             BlockdevOnError on_target_error,
1626                             bool unmap,
1627                             BlockCompletionFunc *cb,
1628                             void *opaque,
1629                             const BlockJobDriver *driver,
1630                             bool is_none_mode, BlockDriverState *base,
1631                             bool auto_complete, const char *filter_node_name,
1632                             bool is_mirror, MirrorCopyMode copy_mode,
1633                             Error **errp)
1634{
1635    MirrorBlockJob *s;
1636    MirrorBDSOpaque *bs_opaque;
1637    BlockDriverState *mirror_top_bs;
1638    bool target_is_backing;
1639    uint64_t target_perms, target_shared_perms;
1640    int ret;
1641
1642    if (granularity == 0) {
1643        granularity = bdrv_get_default_bitmap_granularity(target);
1644    }
1645
1646    assert(is_power_of_2(granularity));
1647
1648    if (buf_size < 0) {
1649        error_setg(errp, "Invalid parameter 'buf-size'");
1650        return NULL;
1651    }
1652
1653    if (buf_size == 0) {
1654        buf_size = DEFAULT_MIRROR_BUF_SIZE;
1655    }
1656
1657    if (bdrv_skip_filters(bs) == bdrv_skip_filters(target)) {
1658        error_setg(errp, "Can't mirror node into itself");
1659        return NULL;
1660    }
1661
1662    target_is_backing = bdrv_chain_contains(bs, target);
1663
1664    /* In the case of active commit, add dummy driver to provide consistent
1665     * reads on the top, while disabling it in the intermediate nodes, and make
1666     * the backing chain writable. */
1667    mirror_top_bs = bdrv_new_open_driver(&bdrv_mirror_top, filter_node_name,
1668                                         BDRV_O_RDWR, errp);
1669    if (mirror_top_bs == NULL) {
1670        return NULL;
1671    }
1672    if (!filter_node_name) {
1673        mirror_top_bs->implicit = true;
1674    }
1675
1676    /* So that we can always drop this node */
1677    mirror_top_bs->never_freeze = true;
1678
1679    mirror_top_bs->total_sectors = bs->total_sectors;
1680    mirror_top_bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED;
1681    mirror_top_bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
1682                                          BDRV_REQ_NO_FALLBACK;
1683    bs_opaque = g_new0(MirrorBDSOpaque, 1);
1684    mirror_top_bs->opaque = bs_opaque;
1685
1686    bs_opaque->is_commit = target_is_backing;
1687
1688    bdrv_drained_begin(bs);
1689    ret = bdrv_append(mirror_top_bs, bs, errp);
1690    bdrv_drained_end(bs);
1691
1692    if (ret < 0) {
1693        bdrv_unref(mirror_top_bs);
1694        return NULL;
1695    }
1696
1697    /* Make sure that the source is not resized while the job is running */
1698    s = block_job_create(job_id, driver, NULL, mirror_top_bs,
1699                         BLK_PERM_CONSISTENT_READ,
1700                         BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
1701                         BLK_PERM_WRITE, speed,
1702                         creation_flags, cb, opaque, errp);
1703    if (!s) {
1704        goto fail;
1705    }
1706    bs_opaque->job = s;
1707
1708    /* The block job now has a reference to this node */
1709    bdrv_unref(mirror_top_bs);
1710
1711    s->mirror_top_bs = mirror_top_bs;
1712
1713    /* No resize for the target either; while the mirror is still running, a
1714     * consistent read isn't necessarily possible. We could possibly allow
1715     * writes and graph modifications, though it would likely defeat the
1716     * purpose of a mirror, so leave them blocked for now.
1717     *
1718     * In the case of active commit, things look a bit different, though,
1719     * because the target is an already populated backing file in active use.
1720     * We can allow anything except resize there.*/
1721
1722    target_perms = BLK_PERM_WRITE;
1723    target_shared_perms = BLK_PERM_WRITE_UNCHANGED;
1724
1725    if (target_is_backing) {
1726        int64_t bs_size, target_size;
1727        bs_size = bdrv_getlength(bs);
1728        if (bs_size < 0) {
1729            error_setg_errno(errp, -bs_size,
1730                             "Could not inquire top image size");
1731            goto fail;
1732        }
1733
1734        target_size = bdrv_getlength(target);
1735        if (target_size < 0) {
1736            error_setg_errno(errp, -target_size,
1737                             "Could not inquire base image size");
1738            goto fail;
1739        }
1740
1741        if (target_size < bs_size) {
1742            target_perms |= BLK_PERM_RESIZE;
1743        }
1744
1745        target_shared_perms |= BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE;
1746    } else if (bdrv_chain_contains(bs, bdrv_skip_filters(target))) {
1747        /*
1748         * We may want to allow this in the future, but it would
1749         * require taking some extra care.
1750         */
1751        error_setg(errp, "Cannot mirror to a filter on top of a node in the "
1752                   "source's backing chain");
1753        goto fail;
1754    }
1755
1756    s->target = blk_new(s->common.job.aio_context,
1757                        target_perms, target_shared_perms);
1758    ret = blk_insert_bs(s->target, target, errp);
1759    if (ret < 0) {
1760        goto fail;
1761    }
1762    if (is_mirror) {
1763        /* XXX: Mirror target could be a NBD server of target QEMU in the case
1764         * of non-shared block migration. To allow migration completion, we
1765         * have to allow "inactivate" of the target BB.  When that happens, we
1766         * know the job is drained, and the vcpus are stopped, so no write
1767         * operation will be performed. Block layer already has assertions to
1768         * ensure that. */
1769        blk_set_force_allow_inactivate(s->target);
1770    }
1771    blk_set_allow_aio_context_change(s->target, true);
1772    blk_set_disable_request_queuing(s->target, true);
1773
1774    s->replaces = g_strdup(replaces);
1775    s->on_source_error = on_source_error;
1776    s->on_target_error = on_target_error;
1777    s->is_none_mode = is_none_mode;
1778    s->backing_mode = backing_mode;
1779    s->zero_target = zero_target;
1780    s->copy_mode = copy_mode;
1781    s->base = base;
1782    s->base_overlay = bdrv_find_overlay(bs, base);
1783    s->granularity = granularity;
1784    s->buf_size = ROUND_UP(buf_size, granularity);
1785    s->unmap = unmap;
1786    if (auto_complete) {
1787        s->should_complete = true;
1788    }
1789
1790    s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
1791    if (!s->dirty_bitmap) {
1792        goto fail;
1793    }
1794    if (s->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING) {
1795        bdrv_disable_dirty_bitmap(s->dirty_bitmap);
1796    }
1797
1798    ret = block_job_add_bdrv(&s->common, "source", bs, 0,
1799                             BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE |
1800                             BLK_PERM_CONSISTENT_READ,
1801                             errp);
1802    if (ret < 0) {
1803        goto fail;
1804    }
1805
1806    /* Required permissions are already taken with blk_new() */
1807    block_job_add_bdrv(&s->common, "target", target, 0, BLK_PERM_ALL,
1808                       &error_abort);
1809
1810    /* In commit_active_start() all intermediate nodes disappear, so
1811     * any jobs in them must be blocked */
1812    if (target_is_backing) {
1813        BlockDriverState *iter, *filtered_target;
1814        uint64_t iter_shared_perms;
1815
1816        /*
1817         * The topmost node with
1818         * bdrv_skip_filters(filtered_target) == bdrv_skip_filters(target)
1819         */
1820        filtered_target = bdrv_cow_bs(bdrv_find_overlay(bs, target));
1821
1822        assert(bdrv_skip_filters(filtered_target) ==
1823               bdrv_skip_filters(target));
1824
1825        /*
1826         * XXX BLK_PERM_WRITE needs to be allowed so we don't block
1827         * ourselves at s->base (if writes are blocked for a node, they are
1828         * also blocked for its backing file). The other options would be a
1829         * second filter driver above s->base (== target).
1830         */
1831        iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
1832
1833        for (iter = bdrv_filter_or_cow_bs(bs); iter != target;
1834             iter = bdrv_filter_or_cow_bs(iter))
1835        {
1836            if (iter == filtered_target) {
1837                /*
1838                 * From here on, all nodes are filters on the base.
1839                 * This allows us to share BLK_PERM_CONSISTENT_READ.
1840                 */
1841                iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
1842            }
1843
1844            ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
1845                                     iter_shared_perms, errp);
1846            if (ret < 0) {
1847                goto fail;
1848            }
1849        }
1850
1851        if (bdrv_freeze_backing_chain(mirror_top_bs, target, errp) < 0) {
1852            goto fail;
1853        }
1854    }
1855
1856    QTAILQ_INIT(&s->ops_in_flight);
1857
1858    trace_mirror_start(bs, s, opaque);
1859    job_start(&s->common.job);
1860
1861    return &s->common;
1862
1863fail:
1864    if (s) {
1865        /* Make sure this BDS does not go away until we have completed the graph
1866         * changes below */
1867        bdrv_ref(mirror_top_bs);
1868
1869        g_free(s->replaces);
1870        blk_unref(s->target);
1871        bs_opaque->job = NULL;
1872        if (s->dirty_bitmap) {
1873            bdrv_release_dirty_bitmap(s->dirty_bitmap);
1874        }
1875        job_early_fail(&s->common.job);
1876    }
1877
1878    bs_opaque->stop = true;
1879    bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
1880                             &error_abort);
1881    bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
1882
1883    bdrv_unref(mirror_top_bs);
1884
1885    return NULL;
1886}
1887
1888void mirror_start(const char *job_id, BlockDriverState *bs,
1889                  BlockDriverState *target, const char *replaces,
1890                  int creation_flags, int64_t speed,
1891                  uint32_t granularity, int64_t buf_size,
1892                  MirrorSyncMode mode, BlockMirrorBackingMode backing_mode,
1893                  bool zero_target,
1894                  BlockdevOnError on_source_error,
1895                  BlockdevOnError on_target_error,
1896                  bool unmap, const char *filter_node_name,
1897                  MirrorCopyMode copy_mode, Error **errp)
1898{
1899    bool is_none_mode;
1900    BlockDriverState *base;
1901
1902    GLOBAL_STATE_CODE();
1903
1904    if ((mode == MIRROR_SYNC_MODE_INCREMENTAL) ||
1905        (mode == MIRROR_SYNC_MODE_BITMAP)) {
1906        error_setg(errp, "Sync mode '%s' not supported",
1907                   MirrorSyncMode_str(mode));
1908        return;
1909    }
1910    is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
1911    base = mode == MIRROR_SYNC_MODE_TOP ? bdrv_backing_chain_next(bs) : NULL;
1912    mirror_start_job(job_id, bs, creation_flags, target, replaces,
1913                     speed, granularity, buf_size, backing_mode, zero_target,
1914                     on_source_error, on_target_error, unmap, NULL, NULL,
1915                     &mirror_job_driver, is_none_mode, base, false,
1916                     filter_node_name, true, copy_mode, errp);
1917}
1918
1919BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,
1920                              BlockDriverState *base, int creation_flags,
1921                              int64_t speed, BlockdevOnError on_error,
1922                              const char *filter_node_name,
1923                              BlockCompletionFunc *cb, void *opaque,
1924                              bool auto_complete, Error **errp)
1925{
1926    bool base_read_only;
1927    BlockJob *job;
1928
1929    GLOBAL_STATE_CODE();
1930
1931    base_read_only = bdrv_is_read_only(base);
1932
1933    if (base_read_only) {
1934        if (bdrv_reopen_set_read_only(base, false, errp) < 0) {
1935            return NULL;
1936        }
1937    }
1938
1939    job = mirror_start_job(
1940                     job_id, bs, creation_flags, base, NULL, speed, 0, 0,
1941                     MIRROR_LEAVE_BACKING_CHAIN, false,
1942                     on_error, on_error, true, cb, opaque,
1943                     &commit_active_job_driver, false, base, auto_complete,
1944                     filter_node_name, false, MIRROR_COPY_MODE_BACKGROUND,
1945                     errp);
1946    if (!job) {
1947        goto error_restore_flags;
1948    }
1949
1950    return job;
1951
1952error_restore_flags:
1953    /* ignore error and errp for bdrv_reopen, because we want to propagate
1954     * the original error */
1955    if (base_read_only) {
1956        bdrv_reopen_set_read_only(base, true, NULL);
1957    }
1958    return NULL;
1959}
1960